The present invention relates to a flame atmosphere analyzer according to the preamble to the main claim.
The invention also relates to a water-heating device including the analyzer.
The invention concerns, in particular but not exclusively, the field of flame atmosphere analyzers used for piloting the lighting of gas burners provided in storage water heaters for heating water for hygiene purposes.
These analyzers are preferred to other known devices because of the safety functions which typically characterize them. They are in fact used not only for lighting the main burner and for stopping the gas supply to the burner when the flame goes out and/or when the pressure falls below a safety threshold, but also for intervening to cut off the gas supply when the oxygen content of the combustion air falls below a safety value or, conversely, when the carbon-dioxide content rises. To ensure this greater sensitivity, these atmosphere analyzers have dimensions suitable for the use of air-gas mixing ratios such as to give rise to a fairly unstable flame which is susceptible to detachment upon variations in the oxygen content of the air.
In the specific field of storage water heaters for heating water for hygiene purposes, it is known to use these devices in areas such as, for example, garages, which are intended for the parking of motor vehicles and/or for the storage of inflammable materials such as oils, solvents, paints and similar substances. In these cases, liquids or vapours due to leakages of these substances from the storage containers or to leakages of fuel from the motor vehicles may be set on fire by the flame which is present in the burner of the water heater, with dangerous consequences.
To solve this problem at least partially, the prior art has proposed the introduction of special flame-arresting grids in the openings for admitting air to the combustion chambers of water heaters. These grids have very fine mesh configurations which confine the flame within the combustion chamber, preventing it from spreading outside the water heater and consequently being propagated in the surrounding environment.
The main limitation encountered in this proposed solution is due to the fact that dust, hair, and other xe2x80x9cdirtxe2x80x9d which is normally present in such environments may obstruct these flame-arresting grids, resulting in a worsening of the combustion characteristics, for example, owing to a high level of carbon monoxide (CO) production, and the occurrence of possible functional problems in the water heater, which are connected, for example, with the production of soot, with partial obstruction of the ducts for evacuating discharge fumes, or with possible flare-ups. Naturally, all of this may lead to conditions dangerous to people who are in the vicinity of the environment surrounding the water heater.
The problem underlying the present invention is that of providing a flame atmosphere analyzer, as well as a water-heating device including the analyzer, which have structural and functional characteristics such as to overcome the limitations encountered with reference to the prior art mentioned.
This problem is solved by the invention by means of a flame atmosphere analyzer and a water-heating device including the analyzer which are formed in accordance with the appended claims.